Split BotServ and MemoServ into one-file-per-command modules

Match the NickServ/ChanServ layout: lib.rs keeps only the service struct
and the on_command dispatcher, and each command moves to its own file
bridged with #[path]. No behaviour change.

BotServ: bot.rs, assign.rs.
MemoServ: send.rs, list.rs, read.rs, del.rs.

memoserv/src/read.rs

@@ -0,0 +1,42 @@
+use fedserv_api::{human_time, MemoView, Sender, ServiceCtx, Store};
+
+// READ <num>|NEW|ALL: display memos and mark them read.
+pub fn handle(me: &str, from: &Sender, account: &str, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    match args.get(1).map(|s| s.to_ascii_uppercase()).as_deref() {
+        Some("NEW") | Some("ALL") => {
+            let only_new = args[1].eq_ignore_ascii_case("new");
+            let targets: Vec<usize> = db
+                .memo_list(account)
+                .iter()
+                .enumerate()
+                .filter(|(_, m)| !only_new || !m.read)
+                .map(|(i, _)| i)
+                .collect();
+            if targets.is_empty() {
+                ctx.notice(me, from.uid, if only_new { "You have no new memos." } else { "You have no memos." });
+                return;
+            }
+            for i in targets {
+                if let Some(m) = db.memo_read(account, i) {
+                    show(me, from, i, &m, ctx);
+                }
+            }
+        }
+        Some(numstr) => {
+            let Some(n) = numstr.parse::<usize>().ok().filter(|n| *n >= 1) else {
+                ctx.notice(me, from.uid, "Syntax: READ <num>|NEW|ALL");
+                return;
+            };
+            match db.memo_read(account, n - 1) {
+                Some(m) => show(me, from, n - 1, &m, ctx),
+                None => ctx.notice(me, from.uid, format!("You have no memo #\x02{n}\x02.")),
+            }
+        }
+        None => ctx.notice(me, from.uid, "Syntax: READ <num>|NEW|ALL"),
+    }
+}
+
+fn show(me: &str, from: &Sender, index: usize, m: &MemoView, ctx: &mut ServiceCtx) {
+    ctx.notice(me, from.uid, format!("Memo #\x02{}\x02 from \x02{}\x02 ({}):", index + 1, m.from, human_time(m.ts)));
+    ctx.notice(me, from.uid, format!("  {}", m.text));
+}